The present invention relates to the field of instrumented rolling bearings equipped with an assembly for detecting rotation parameters such as the angular position, the direction of rotation, the speed and the acceleration.
Such instrumented rolling bearings and such set-ups are well known, particularly from document FR 2 754 903. These instrumented rolling bearings can be used, for example, for controlling electric motors of the synchronous type.
The detection assembly consisting of a sensor unit and an encoder element then supplies the motor control system with all the information it needs, particularly the rotational speed and the position of the poles of the rotor with respect to those of the stator. The rotor may be equipped with an encoder delivering pulses and the stator may be equipped with a stationary sensor capable of detecting these pulses and of deducing them from the information that relates to the movement and to the angular position of the rotor with respect to the stator. In conventional set-ups, the sensor-encoder system is independent of the rolling bearings via which the rotor rotates in the stator concentrically with the latter.
In a way known per se, the encoder may be of the magnetic type, and may be in the form of a multipole ring, the number of poles of which depends on the number of poles of the motor that is to be controlled. The encoder may collaborate with a sensor of the type sensitive to magnetism, for example a Hall-effect probe, delivering an output voltage that varies each time the polarity of the encoder ring changes, and thus delivering a characteristic signal of the square-wave type.
If there is a desire to determine the position of the poles of the rotor with respect to those of the stator using the instrumented rolling bearing, it will be appreciated that it is necessary, when mounting the rotor in the stator, for:
the sensor to be oriented angularly with respect to the poles of the stator,
the encoder to be oriented angularly with respect to the sensor,
the encoder to be oriented angularly with respect to the poles of the rotor.
These operations are relatively tricky to perform in that they need to be carried out simultaneously while the rotor is being mounted in the stator.
The invention proposes an instrumented rolling-bearing device arranged in place of one of the two rolling bearings, thus avoiding the mounting of a separate sensor-encoder assembly in the motor, the rolling-bearing device being pre-indexed so as to eliminate the operation of indexing the encoder with respect to the sensor when assembling the motor.
The instrumented rolling-bearing device, according to one aspect of the invention, is of the type comprising an outer ring, an inner ring, at least one row of rolling elements which are arranged between a raceway of the outer ring and a raceway of the inner ring, and an assembly for detecting rotational parameters comprising a sensor unit secured to the non-rotating ring and supporting a sensor element, and a rotary encoder member forming, with the rotating ring, a rotating part, the encoder member comprising an active part rotating past the sensor element, the sensor unit and the non-rotating ring forming a stationary part. The rotating part comprises an indexing means external to the active part of the encoder member and capable of angularly positioning said rotating part with respect to a reference of the stationary part in a position in which the encoder generates a reference signal in the sensor element.
xe2x80x9cExternalxe2x80x9d is to be understood here as meaning separate.
Thus, the motor manufacturer need now concern himself only with the angular orientation of the rotor with respect to the stator, all the other angular indexing operations being performed by direct mechanical means.
In one embodiment of the invention, the indexing means is supported by an intermediate part secured to the rotating part.
Advantageously, the intermediate part is a sleeve secured to the rotating ring.
In one embodiment of the invention, the sleeve is removable from the rotating ring.
In another embodiment of the invention, the indexing means is formed directly on the rotating ring, or on the encoder member.
Advantageously, the indexing means consists of a protrusion, a groove, a notch or an optical mark.
In one embodiment of the invention, a terminal for leading wires out of the sensor unit comprises the reference of the stationary part used for the angular positioning of the means of indexing of the rotating part.
In one embodiment of the invention, the indexing means and a terminal for leading wires out of the sensor unit are aligned when the encoder delivers the reference signal in the sensor.
As a preference, the encoder, for example its annular support, is provided with an angular indexing means capable of collaborating with a manufacturing tool, such as a mold. The indexing means may be a notch.
In one embodiment of the invention, the indexing means also forms a reference means when producing the active part of the encoder.
The present invention also proposes a method of pre-indexing a device as described hereinabove, in which method the rotating part is rotated until the reference signal is delivered, the two parts, rotating and stationary, are immobilized in this relative angular position, and an indexing means is placed on the rotating part in a given angular position with respect to a reference of the stationary part.
In the case of an instrumented rolling bearing mounted in a synchronous motor, precise angular indexing of the sensor with respect to an element of the casing whose angular position with respect to the stator is known makes it possible, if the encoder is itself indexed with respect to the shaft and with respect to the poles of the rotor, to determine the angular position of the rotor with respect to the stator and therefore the relative position of the poles. The sensor-encoder assembly can furthermore deliver information relating to the speed and to the acceleration of the rotor.
The invention also proposes a method in which the encoder support is positioned angularly in a mold and the active part is magnetized while it is being overmolded.
Alternatively, it is also possible for the encoder to be positioned angularly with respect to a magnetizing system, and then for the active part to be magnetized. In both cases, the poles will still arranged in a repeatable way with respect to an indexing means.